Wetness sensors, wetness monitoring system, and related methods

ABSTRACT

An aspect of the invention is a liquid sensor having a galvanically energizable power source capable of activating a remotely detectable signal in response to liquid. In a preferred embodiment, a liquid sensor includes a plurality of electrodes, a circuit, and a transmitter thereon. The electrodes are coupled to generate electrical power when in contact with liquid. The circuit is electrically connected to the electrodes so as to be activated by the electrical power, detect an electrical parameter of the electrical power, and generate a plurality of data packets indicating a degree of wetness corresponding to the detected electrical parameter. The transmitter is electrically coupled to the circuit to receive the plurality of data packets and transmit representations of the plurality of data packets as electromagnetic signals. Other aspects include a liquid absorbent wetness sensor and a computer-based wetness monitoring system, and method of detecting liquid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 14/233,564, filed Feb. 11, 2014, which is anational stage application of International Application No.PCT/US2012/047712, filed Jul. 20, 2012, which claims priority to U.S.provisional Application No. 61/509,774, filed Jul. 20, 2011 and titled“A Self-Powered Disposable Wetness Sensor and Response System andRelated Methods” and U.S. provisional Application No. 61/512,071, filedJul. 27, 2011 and titled “A Self-Powered Disposable Wetness Sensor andResponse System and Related Methods,” all of which are herebyincorporated by reference in their entireties.

FIELD OF THE INVENTION

This invention relates to liquid sensors capable of transmittingremotely detectable signals. More particularly, it relates to liquidsensors with improved signal transmission properties and improved liquidflow management properties.

BACKGROUND

Enuresis, or urinary incontinence (UI), is a health condition affectingmany individuals. It is the leading cause of patient admission to along-term care facility. UI can lead to a variety of medical problemsthat dramatically increase the cost of care. As a result of prolongedexposure to moisture from UI, perianal skin damage occurs and canprogress rapidly to ulceration and secondary infection, includingbacterial and yeast infections that increase discomfort and treatmentcosts. The standard of care required in most long-term care facilitiesis to check each patient at least every two hours and change them whenneeded. While this practice ensures a patient should go no longer thantwo hours without attention, it still leaves as much as a two hourwindow of wetness exposure should the patient wet shortly following aninitial check, putting patients at significant risk of skin breakdownand disrupted sleep during the night. This method also requires staff towaste time checking patients who do not need assistance.

SUMMARY

Although many liquid detecting sensors capable of remotely alerting acaregiver, via radio frequency signals, when a wetness event occurs areknown, many of them suffer from drawbacks related to the way the signalsare transmitted between the sensors and detectors and the way liquid istransported to the sensor. They also do not provide the ability todetermine the degree of wetness or the type of liquid in proximity tothe sensor.

The inventors have devised a self-powered powered wetness sensor thatuses the liquid to power the sensor's electronics. The sensor'selectronics are also configured to include representations of theseelectrical parameters in the data transmission. Because the electricalparameters vary depending on the degree of wetness and/or type ofliquid, the sensors are able to provide this valuable information.

In a preferred embodiment of the sensor, these advantages are achievedby providing a sensor comprising a substrate having a plurality ofelectrodes, a circuit, and a transmitter thereon. The plurality ofelectrodes are coupled to generate electrical power when in contact withliquid. The circuit is electrically connected to the electrodes so as tobe activated by the electrical power, detect an electrical parameter ofthe electrical power, and generate a plurality of data packetsindicating a degree of wetness corresponding to the detected electricalparameter. The transmitter is electrically coupled to the circuit toreceive the plurality of data packets and transmit representations ofthe plurality of data packets as electromagnetic signals.

Another aspect of the invention is a liquid absorbent wetness sensorthat includes one or more of the sensors placed between a plurality oflayers of material that receive liquid discharge, such as urine, from awearer. A preferred embodiment of the liquid absorbent wetness sensorcomprises a liquid transport layer positionable next to the skin of awearer and capable of transporting a volume of liquid discharged by thewearer away from the wearer's skin; a liquid absorbent layer thatreceives the transported liquid; and a liquid sensor in liquidcommunication with the liquid absorbent layer. The liquid sensorcomprises a galvanically energizable power source capable of activatinga remotely detectable signal in response to liquid in the liquidabsorbent layer. A liquid management layer is positioned between theliquid transport layer and liquid absorbent layer. The liquid managementlayer comprises a material that retards liquid flow between the liquidtransport layer and liquid absorbent layer so as to prevent the sensorfrom being energized until the volume of liquid is large enough to flowto the liquid absorbent layer and energize the power source. Here, theliquid management layer is particularly advantageous as it prevents thesensor from being activated unless a substantial wetness event occurs.

In yet another aspect of the invention, the sensor is included in awetness monitoring system in which one or more transceivers are adaptedto receive the plurality of data packets and communicate data over acommunication network to an electronic database. The electronic databaseforms part of a control computer system that can alert a monitoringagent, such as a caregiver, if wetness is sensed. Thereby, allowing themonitoring agent to quickly address the issue.

In a method aspect of the invention, a preferred method of detectingliquid comprises detecting the presence of liquid in proximity to asensor, the sensor having a substrate with a plurality of electrodes, acircuit, and a transmitter positioned thereon. The electrodes arecoupled to generate electrical power when in contact with liquid. Thecircuit is electrically connected to the electrodes so as to beactivated by the electrical power, detect an electrical parameter of theelectrical power, and generate a plurality of data packets indicating adegree of wetness corresponding to the detected electrical parameter.The method further comprises receiving a transmitted signal from thesensor, the signal including representations of the plurality of datapackets. Other features of the include determining an amount of liquidin proximity to the electrodes by correlating the detected electricalparameter with a wetness value and/or determining a type of liquid inproximity to the electrodes by correlating the detected electricalparameter with a liquid type.

These and other aspects, embodiments, and advantages of the inventionwill be better understood by viewing the drawings and referring to thefollowing discussion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a first embodiment of wetness sensor incombination with a detector in accordance with an aspect of theinvention;

FIG. 2 is a top plan view of the first embodiment of the wetness sensorin accordance with an aspect of the invention;

FIG. 3 is a side elevation view of the wetness sensor of FIG. 2;

FIG. 4 is a top plan view of a second embodiment of a wetness sensor inaccordance with an aspect of the invention;

FIG. 5 is a side elevation view of the wetness sensor of FIG. 4;

FIG. 6 is an exploded view of a first embodiment of a sensor assembly,highlighting its method of construction in accordance with an aspect ofthe invention;

FIG. 7 is a side cross-sectional view of a second embodiment of a sensorassembly in accordance with an aspect of the invention;

FIG. 8 is a side cross-sectional view of a third embodiment of a sensorassembly in accordance with an aspect of the invention;

FIG. 9 is a top exploded view of a fourth embodiment of a sensorassembly in accordance with an aspect of the invention, in which the toplayer is cut-away to provide a better view of the liquid managementlayer;

FIG. 10 is a side cross-sectional view of the sensor assembly of FIG. 9;

FIG. 11 is a top exploded view of a fifth embodiment of a sensorassembly in accordance with an aspect of the invention, in which the toplayer and an acquisition and distribution (ADL) layer are cut-away toprovide a better view of the elongated sensor;

FIG. 12 is a top perspective view of the interior of a diaper having asensor assembly thereon in accordance with an aspect of the invention;

FIG. 13 is a top perspective view of the interior of a diaper having twosensor assemblies thereon in accordance with an aspect of the invention;

FIG. 14 is a top exploded view of a sixth embodiment of a sensorassembly in accordance with an aspect of the invention, in which the toplayer, liquid management layer, and ADL layer are cut-away to provide abetter view of the elongated sensor;

FIG. 15 is a diagram of a person wearing an undergarment in the form ofa diaper having a wetness sensor attached thereto in accordance with anaspect of the invention;

FIG. 16 is a top exploded view of a portion of an undergarment having asensor assembly installed therein in accordance with an aspect of theinvention, in which the top four layers are cut-away to provide a betterview of the elongated sensor;

FIG. 17 is a top exploded view of a portion of another undergarmenthaving a sensor assembly installed therein in accordance with an aspectof the invention, in which the top two layers are substantially cut-awayto provide a better view of the ADL layer, which is partially cut-awayto so that the sensor can be seen;

FIG. 18 is schematic of a wetness monitoring system in accordance withan aspect of the invention;

FIG. 19 is a flow diagram of an initialization protocol, which is anaspect of the wetness monitoring system;

FIG. 20 is a flow diagram of a user preparation protocol, which is anaspect of the wetness monitoring system;

FIG. 21 is a flow diagram of a wetness detection and reporting protocol,which is an aspect of the wetness monitoring system;

FIG. 22 is a flow diagram of a wetness alert protocol, which is anaspect of the wetness monitoring system;

FIG. 23 is a side elevation view of a liquid collection bag including aplurality of wetness sensors for measuring the amount of liquid in thebag in accordance with an aspect of the invention;

FIG. 24 is a side elevation view of a wound dressing including a wetnesssensor in accordance with an aspect of the invention; and

FIG. 25 is a top plan view of the wetness sensor embodiment of FIGS. 2and 3, showing coated leads.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the Summary above and in the Detailed Description of PreferredEmbodiments, reference is made to particular features (including methodsteps) of the invention. Where a particular feature is disclosed in thecontext of a particular aspect or embodiment of the invention, thatfeature can also be used, to the extent possible, in combination withand/or in the context of other particular aspects and embodiments of theinvention, and in the invention generally.

The term “comprises” is used herein to mean that other ingredients,features, steps, etc. are optionally present. When reference is madeherein to a method comprising two or more defined steps, the steps canbe carried in any order or simultaneously (except where the contextexcludes that possibility), and the method can include one or more stepswhich are carried out before any of the defined steps, between two ofthe defined steps, or after all of the defined steps (except where thecontext excludes that possibility).

In this section, the invention will be described more fully withreference to certain preferred embodiments. This invention may, however,be embodied in many different forms and should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will convey preferred embodimentsof the invention to those skilled in the art.

Before describing the specific aspects and preferred embodiments of theinvention in detail, some of the general principles related to theinvention are first discussed. A particularly important aspect of theinvention is a compact self-powered wetness sensor that may beincorporated into an insert that can be placed inside undergarments suchas diapers or briefs to detect wetness therein. The sensor mayalternatively be integrated with the undergarment.

In an institutional setting, such as a hospital or convalescent home,the sensor may be attached to patients who suffer from incontinence sothat wet diapers, for example, can quickly be addressed by the patients'caregivers. In such settings, an electronic transceiver may be assignedto each sensor being monitored or to a specific location or room. Thetransceiver contains wireless reception and transmission electronics andis battery powered. The transceiver may be placed remote from thepatient or attached to the patient. If the transceiver is attached tothe patient, it may be desirable to include a temperature sensor, anaccelerometer, a GPS receiver or other geographic location unit todetect the patient's movement and orientation. A single transceiver canpreferably communicate with multiple sensors.

The transceiver may also communicate with a computer database viastandard wireless protocol and identify its location and item beingmonitored. The computer system associated with the database acknowledgesthe transmission and establishes or continues a data file dedicated tothat item. The data file includes each transmission's purpose plus thetime and date of the transmission. Examples of “transmission purposes”include but are not limited to: sensor has been installed, low receiverbattery, accelerometer inactivity, excessive or unexpected accelerometermovement, degree of wetness, “wetness threshold reached” alert, finaltransmission from a sensor, initial transmission from a sensor, patientlocation information, movement outside allowed range, and/or patientrequires assistance. This information may then be made available forreview electronically by any device with authorization for access tothat data.

When the item being monitored experiences a liquid insult, the sensors'galvanic cell is activated by the liquid, thereby providing power to thesensor's electronics. After a delay for sensor stabilization and powerintegration, the sensor begins transmitting data packets at timedintervals proportional to the wetness being sensed or transmitsinformation about the wetness-dependent analog output of the galvaniccell, including but not limited to voltage, amperage, impedance, orcapacitance. The data bursts may include a sensor identification codewhen applicable. The transceiver previously assigned to this sensorreceives the data burst, identifies the sensor, initiates the local datatable, and records the actual first moment of liquid detection in thedatabase.

The transceiver then attempts to relay this information wirelessly tothe database assigned to this item. If the transceiver is not withinrange of a communications network, it will periodically resend the datauntil an acknowledgement is received from the computer system. New eventdata will cause the transceiver to transmit additional data. The datamay include the amount of fluid leaked, the general type of fluidleaked, and the number of incidences.

Meanwhile, the sensor continues to periodically send data packets,repeating the sensor wetness information. Several methods of sendinginformation from the sensor are feasible. In one embodiment, theinformation related to the sensor is transmitted via inter-pulse timing.The pulse rate will be faster when more liquid is detected. For example,if the sensor experiences additional liquid insult, the period betweenbursts is reduced and the transceiver records this as an additionalwetness event. The transceiver then transmits this new data to thedatabase. In another embodiment, the analog value corresponding to thedegree of wetness received from the sensor is transmitted digitally tothe transceiver. Many different protocols or transmission methods arepossible between the sensor and transceiver. The sensor transmits datavia RF transmission or fluid conduction. The conduction mechanismoperates through the use of small amplitude electrical bursts that canbe read by the detector with conductive pads in contact with the samefluid as the sensor.

Since the transmitted information is typically very small, it can betransmitted very rapidly, for example in microseconds. In oneembodiment, multiple sensors communicate simultaneously with the use ofcommunications slots through an anti-collision protocol. The transceivertransmits a clock signal with periodic information indicating the startof the first slot. Each sensor that detects this timing informationrandomly selects a slot and communicates its information during thistime period. Since the number of slots can be very large (easily 1000while maintaining efficient communication throughput), the random chanceof any two sensors selecting the same slot is essentially zero. Whencommunication is properly received by the receiver, it can sendinformation to the sensor indicating that the information was receivedproperly. If the sensor does not receive this handshake, the sensor maybe colliding with another sensor and can randomly select another slot.As known in the art, many other methods of using two-way communicationto allow communication of multiple senders of information are possible.

When integrate and fire communication is utilized, the system leveragesthe small burst size relative to the total time available to transmit.In a one-way communication scenario, the sensors send data packets atrandom start times and the receiver partitions the pulse trains withvarious algorithms. One such suitable algorithm called “independentcomponent analysis” looks for patterns in the repetitive nature of thesignals and finds the independent sources without knowledge of thenumber of sources or the identity of the sources. With two waycommunication and integrate and fire communication, the data packets canbe synchronized to slots defined by the transceiver's clock signal. Datapackets are integrated until a threshold is reached and then thetransmission occurs only when its assigned (randomly or by the masterreceiver) slot arrives next.

The sensor preferably has a generally planar form factor, with small 3Dfeatures defining the sensor circuitry, such as metallization areas, anelectronic bursting circuit, various coatings, and the like. Thegenerally planar geometry allows the system to be used in a number ofapplications, such as those described herein. The sensor may be fullythree-dimensional to help facilitate signal directionality, allow forfluid management structures, or allow for more appropriate placement.

The various aspects and embodiments of the invention have manyadvantages. Some but not all of those advantages are now described. Notevery aspect and/or embodiment of the invention is require to achieveall of these advantages.

The wetness sensor itself has many advantages. Because it is onlyactivated through liquid contact it has a nearly unlimited shelf life.Some embodiments of the sensor are compact, flexible, and disposable.

Liquid flow control techniques used in certain embodiments of the sensorassemblies use a unique combination of standard diaper materials todirect the flow of liquid to or from the sensor as needed. This allowslarge areas to be monitored with the minimum number of sensors.

Integrate and fire RF technology allows for battery-less operation(energy harvesting) while allowing enhanced range of detection. It alsoprovides for enhanced data transmission by incorporating information inthe pulse timing of the data stream.

The cost of making the sensors is exceptionally low, which makes thesensors more amenable to being disposed of after user.

A more detailed description of these aspects and embodiments of theinvention are now discussed.

A. Wetness Sensor

Referring initially to FIG. 1, a self-powered wetness sensor 10 a inaccordance with an embodiment of the invention self-generates theelectrical power needed to operate its circuitry when it comes intocontact with a conductive liquid L. The sensor's circuitry uses thispower to transmit an electromagnetic signal 12 to a remoteelectromagnetic detector 14. The signal 12 includes information aboutthe wetness event that generated the conductive liquid L. Additionaldetails of the sensor 10 a and an alternate embodiment thereof are nowdescribed in connection with FIGS. 2-5.

The wetness sensor 10 a embodied in FIGS. 2 and 3, includes a substrate20 with sensor electronics 22 located thereon. The sensor electronics 22include a galvanic cell 24 equipped with a first conductive lead 26 anda second conductive lead 28. The conductive leads 26, 28 of the galvaniccell 24 are in electrical contact with an integrated circuit 30, whichis in electrical contact with an antenna 32. An electrically insulatinglayer 34 is placed over the sensor electronics 22, but leaving thegalvanic cell 24 exposed. While not always required, an attachmentmember 36 for attaching the sensor 10 a to a desired surface may beplaced on the side of the sensor 10 a opposite the sensor circuitry 22as represented in FIG. 2. Suitable attachment members 36 includeadhesives, adhesive tapes, hook and loop-type fasteners, or the like.

The sensor 10 a may be constructed very small or very large, dependingon what is desired. For many applications, it is desirable to use verysmall sensors having dimensions on the order of centimeters ormillimeters. In a preferred embodiment, the sensor 10 a is about 2 cmalong its length and about 1 mm thick.

Referring now to FIGS. 4 and 5, a sensor 10 b having an increasedwetness detection area A, according to an embodiment of the invention,includes a substrate 20, sensor circuitry 22, galvanic cell 24 equippedwith a first conductive lead 26 and a second conductive lead 28,integrated circuit 30, antenna 32, and electrically insulating layer 34;all of which are configured to operate in the same fashion. Thesubstrate 20, however, is elongated to accommodate a plurality ofconductive lead extensions 40. The conductive lead extensions 40 are inelectrical contact with the leads 26, 28 such that, when the leadextensions 40 come into contact with a conductive liquid, the galvaniccell 24 generates electricity.

The substrate is preferably made of a thin flexible material, includingvarious polymers. Examples of suitable materials include, but are notlimited to, polyesters, polyolefins, polyimides, acrylics, vinyls, andpapers.

The electrically insulating layer is preferably made of a thin flexiblematerial, including various polymers. Examples of suitable materialsinclude, but are not limited to, ethylcellulose, epoxies, silicone, andPETE (TEFLON).

In either embodiment of the sensor 10 a,b The galvanic cell 24self-powers the sensor 10 a,b when it becomes wet with a conductiveliquid, which may include bodily liquids such as urine, blood, or anyother ion containing liquid, for example. This is because the conductiveliquid forms electrical contact between the conductive leads 26,28.

In a preferred embodiment, the galvanic cell 24 b creates a measurableanalog output such as current, voltage, or resistance in various wetnesssituations. When wet, the galvanic cell 24 supplies electrical power tothe sensor 10 a,b. The galvanic cell 24 will begin powering theintegrated circuit 30 as soon as it is wetted. This, in turn, operatesthe antenna 32 which transmits the electromagnetic signal 12 that can beread by the electromagnetic signal detector 14.

The conductive leads 26,28 are preferably made of different metals orcompounds having different reduction/oxidation potentials similar to theanode and cathode of a battery. When the conductive leads 26, 28 areplaced in a conductive liquid, an electric voltage and current aregenerated. The materials used to make the leads 26, 28 may be chosenfrom any number of metals and/or conductive carbon-based inks. Preferredfirst conductive lead 26/second conductive lead 28 combinations include:carbon-based ink/zinc, silver/zinc, copper/zinc, silver/magnesium,copper/magnesium or the various salts thereof (silver chloride or silverphosphate, for example).

If desired, metals used for the leads 26,28 can be transformed by anumber of chemical or physical reactions to produce a new chemicalcompound or material state/character (phase, crystallinity, surfacetexture). By way of example, silver may be transformed to silverphosphate by electrostatically applying a positive voltage to a silverfilm in the presence of phosphate ions. Thus, a silver phosphate cathodemay be used with a zinc anode to form a galvanic cell. The new compoundyields a change the differential voltage compared to non-transformedelectrodes. Magnesium and zinc can be combined by vapor deposition orother methods to create a magnesium/zinc anode. Taking advantage ofother changes in the lead 106,108 are also contemplated. These changesinclude: phase transitions, state transitions, structural changes, andother materials transitions that cause a change in the electrical outputof the galvanic cell. Transformation can occur on the anode or cathodeof the galvanic cell.

For high peak current loads, additional capacitance may be added to thesensor circuitry 22. The capacitance can be added to the integratedcircuit 30 the sensor itself 10 a,b, or the substrate 20. For example,the printed tracings between the galvanic cell 24 and the integratedcircuit 30 may contain two printed metallic plates separated by adielectric that produces a capacitance that will store sufficient chargeto handle the peak current loads. Other methods of adding capacitanceare also possible.

The galvanic cell's 24 source resistance or voltage may be used a gaugeof the amount of wetness in the vicinity of the sensor 10 a,b. Thecurrent draw will begin to pull the galvanic cell 24 voltage below thepeak operating voltage in two scenarios: (1) when the galvanic cell 24is loaded down at its output at the integrated circuit 30, and/or (2)when the amount of conductive liquid is insufficient to maintain theelectrochemical reaction between the leads 26,28. Either or bothscenarios will yield an output voltage and, therefore, the determinedsource resistance, that varies with the amount of liquid presented tothe sensor 10 a,b. The cell voltage is a function of the nature of theionic fluid and the degree of wetness connecting the leads 26,28. Inaddition to any instantaneous wetness, by the use of liquid flowcontrol, the amount of liquid connecting the leads 26,28 can be made todissipate over time. The degree of wetness of the surroundingenvironment of the galvanic cell 24 can affect the speed at which theliquid dissipates in the immediate area of the galvanic cell 24. As theliquid dissipates, the galvanic cell's 24 internal resistance increasesand can be used as an indicator of wetness. The degree of wetness andthe dissipation phenomenon are converted to a proportional time intervalspacing of transmitted data packets.

The voltage produced by the galvanic cell 24 may also be influenced bythe galvanic cell's 24 geometry. For example, elongated parallel cellleads 26,28 produce a real resistance change in the galvanic cell 24when exposed to the conductive liquid. As the liquid comes into contactwith the sensor 10 a,b, the leads 26,28 become increasingly wetted andcapable of generating current. The current or voltage at a given wettedarea can then be measured. The output voltage for the galvanic cell 24is then measured by the integrated circuit 30.

Accordingly, the galvanic cell's 24 voltage, current, and/or resistanceprovide valuable data points that can be used to infer the degree ofwetness in the vicinity of the sensor 10 a,b. In order to be useful,however, these data are preferably transmitted from the antenna 32 tothe detector 14. In practice, the integrated circuit 30 transmits thisinformation to the detector via the antenna 32 using data bursts at agiven time period. A data packet's characteristics are dependent on theinput voltage from the galvanic cell 24. Other suitable methods forcommunicating this data from the sensor 10 a,b to the detector 14include digital methods and conventional methods that vary frequency oramplitude.

The chemically or physically altered leads 26,28 may also be used todistinguish different conductive liquids. Differing wetness liquids, bytheir ionic concentration and/or atomic composition, may alter theoutput electrical characteristic of the galvanic cell 24. For example,the galvanic cell 24 in the presence of urine may produce only 1 V, butin the presence of spilled juice it may produce 1.4 V. Likewise, thecurrent or internal resistance of the galvanic cell 24 may changedepending on the type of wetness.

In this context, a particularly advantageous use of the sensor 10 a,b isas a diaper wetness sensor. In this case, the galvanic cell 24 may beused to discriminate between urine and spilled beverages and transmit asignal to the detector 14 only in response to urine.

The integrated circuit, 30 measures the voltage across the leads 26,28and generates a signal 12 that is transmitted to the detector 14 ifand/or when the target electronic reading is reached in the vicinity ifthe wetness source. If the sensor 10 a,b is not close enough to thewetness source, the voltage will not change appreciably as no chemicaltransformation will proceed. Thus, the voltages can be transmitted viathe sensor 10 a,b to the detector 14 to confirm the that liquid detectedis one of concern.

Conventional wetness sensors are typically highly complex when designedfor analyte specificity or are too simplistic and therefore notanalyte-specific. Material transformation of the leads 26,28 allows forincreased specificity, especially for the limited range of chemicalstypically found in the human body. Furthermore, many pH sensors,potentiometric sensors, actuating sensors, optical/fluorescent sensors,or otherwise require power to analyze incoming signals. Being a systemthat requires no input energy (and can in fact power a cell in itself),our materials transformation wetness sensor keeps parts and designcomplexity to a minimum. For additional capabilities, sensors thatrequire only microamps of current are also suitable, as they can derivepower from the galvanic cell 24 a,b.

The sensor 10 a,b may store energy that allows it to use the galvaniccell 24 in a manner that measures resistance or capacitance or testvarious species using simple coatings. The sensor 10 a,b may be coatedwith one or more coatings selective to ions, molecules,electropotential, polarity, charge, or solvents. In an exemplaryembodiment, a polyurethane coating that is selective for chloride ionsis coated over the leads 26,28 allowing the sensor 10 a,b to be used forchecking for the presence of salts such as those found in incontinenceevents or for impurities in drinking water.

Urease may be used as an analyte-selective electrochemical sensor toproduce an added electrical impulse in the presence of the urea in urinewhen used in conjunction with various field effect transistors (FETs).

In yet another exemplary embodiment, the leads 26,28 are coated with amaterial that only dissolves in the presence of certain desired liquids.

Referring to FIG. 25, the sensor 10 a includes a coating 412 placed overthe leads 26,28.

The voltage output of the galvanic cell 24 can be measured by theintegrated circuit 30 and transmitted to the detector 14 as part of adata packet that indicates the type of liquid encountered and/or thedegree of wetness.

The integrated circuit 30 implements a very low power, low bandwidthcommunications circuit that requires low voltage (˜1 V) and low power(˜10 uW). Input power can be supplied by a variety of energy harvestingtechniques.

In some instances, the voltage level of the galvanic cell 24 may nothave sufficient dynamic range to determine accurate sensor information(e.g. wetness). By placing a resistive load inside or outside the sensorcircuitry 22, the voltage level can be modified to provide betterinformation from the sensor 10 a,b. In some cases, it may be desirableto toggle the resistive load on and off to allow power to flow freely tothe sensor circuitry 22 during normal operation but to add the resistiveload only when the voltage level is being measured.

A drawback to using the very small galvanic cells 24 is that there aresignificant limits to obtaining steady-state voltage and current. Toovercome this drawback, an energy harvesting technique, called“integrate and fire” has been chosen by the inventors as the preferredsignaling method. Conventional RF output signaling requiressignificantly more power than a small galvanic cell can generate but theamount of information that must be transmitted can be done so in a veryshort period of time, typically within microseconds. The design goalsmet using the integrate and fire technology allow for a 1000 to 1benefit in transmission burst output power.

The voltage output of the galvanic cell 24 can also be used to directlymodulate or modify the signal being transmitted to the detector. In apreferred embodiment, using the “integrate and fire” methodology, theburst rate of the sensor 10 a,b is modified by the voltage level of thegalvanic cell 24. An analog circuit including resistors, capacitors, andtransistors is used to store the electrical power generated by thegalvanic cell 24 until a threshold value is met. Once the thresholdvalue is met, the electrical power is released to power the sensorcircuitry 22 and thereby transmit the signal burst. The integrate andfire technique facilitates ultra-low power transmission capabilitieswhile allowing valuable information to be incorporated in theconfiguration of the transmitted data stream. The integrate and firetechnique has multiple objectives, including providing a sensor 10 a,bhaving ultralow power consumption, low cost, and a very small formfactor.

The “integrate and fire” transmission techniques utilized hereinachieves the ultralow power transmission in relatively high RF noiseenvironments. This technique is practical because the amount of databeing transmitted is relatively small while the time available totransmit it is relatively long. In practice, the voltage output of thegalvanic cell 24 powers the integrated circuit 30 and additionallycharges a charge integrating capacitor. While the integrated circuit 30manages the electrical activity, the integrating capacitor is charging.On command from the integrated circuit 30 when a voltage threshold isreached, the charged capacitor is connected to a voltage multiplyingcircuit which drives the antenna 32 with an output pulse durationseveral orders of magnitude shorter than the charge time. The availableRF power in the transmitted pulse is a function of the relative durationof the charge time to the discharge time multiplied by the efficiency ofthe voltage multiplier plus the transmitter circuit.

By monitoring the time duration between pulses, the charge rate of thecharge accumulating capacitor can be determined. If the electrochemicalcell has a high source impedance, indicative of a low degree of wetness,the capacitor takes longer to charge. The time between succeeding RFtransmission bursts therefore is an indication of the degree of wetnessthe sensor 10 a,b is detecting. By utilizing and controlling the timedomain as an indication of transmitted analog data, significantimprovements in ultralow power transmission in high RF noiseenvironments are achieved.

Because the sensor 10 a,b can operate at very low power, it may beembedded in host systems for prolonged periods of time until wetnessactivates the galvanic cell 24, causing the sensor to transmit an RFsignal with a range far exceeding that which passive RFID systems canachieve.

A second objective of the integrate and fire concept adopted herein isto control the time interval between the transmission bursts as anindicator of the value of the input signal being monitored.

Differing voltages or current capabilities of the lead-liquidcombination produce different signal burst rates. Similarly, differentburst lengths, amplitudes, or frequencies can be created based on thevoltage or current of the lead-liquid combination. These methods producea self-powered transmission of the sensor value to an remote detector.These signaling methods are preferably built into the integrated circuit30. Preferably, the integrated circuit 30 circuits electronics that areprinted onto a flexible substrate producing a very small, flexible, andsubstantially planar sensor transmission system.

An alternative approach to self-powering the sensor 10 a,b is a batterythat can be water-activated and embedded in a RFID tag. An example ofsuch a battery is described in U.S. Pat. No. 5,395,707, which disclosesa primary reserve battery useful in sonobuoys on the ocean. The batteryuses cuprous iodide as a cathode and magnesium as the anode in an arrayto provide voltage, amperage, and operational time equivalent toconventional lead chloride batteries. Once the sonobuoy is no longeruseful as it deteriorates in the environment, no lead will be presentedinto the ocean. The structural frame members protect the cuprous iodidewhich is brittle in a rigid array and provides for proper venting of gasand sludge formation to insure efficient operation of the battery.

Other kinds of batteries activated by other liquids like water can befound in the literature. For instance, U.S. Pat. No. 4,185,143 disclosesa water activated battery using a metal/organo-halogen couple whereinthe anode and cathode are formed as planar members with a porousinsulator sandwiched between. There are provided channels to allow theelectrolyte access throughout the cell. The channels may be cut in thecathode or the cathode may be formed as discrete portions of cathodereactant material deposited on a current collector backing plate. Theportions of U.S. Pat. Nos. 5,395,707 and 4,185,143 describing theirrespective batteries is hereby incorporated by reference.

There are also alternate means for sensing the presence of liquid asidefrom the galvanic cell 24. For example, one or more low power sensorsapart from the galvanic cell 24 may be used. A cathode of anode, forexample, that is analyte selective, but is not responsible for providingthe majority of the power are possible to use.

B. Wetness Sensor Assembly

In yet another aspect of the invention, a sensor 10 a,b is incorporatedinto a sensor assembly having components designed to manage the movementof liquid in the vicinity of the sensor 10 a,b.

Sensor assemblies made in accordance with aspects of the inventionemploy unique, yet simple, physical mechanisms for liquid management,utilizing inexpensive materials to gauge liquid levels and controlliquid flow to the sensor 10 a,b as desired.

By placing the sensor 10 a,b in a sensor assembly of the invention, asimple solution to preventing false alarms due to nuisance wetting(sweat, trickles, condensation) is obtained.

The sensor assembly includes a plurality of material layers adapted tocontrol the flow of liquid to the sensor 10 a,b. The materials mayinclude hydrophilic top layers, acquisition and distribution layers,absorbent layers, and non-absorbent backing layers. The sensor assemblymay be made into an insert for a undergarment or diaper or as a femininehygiene pad. Alternatively, it may be incorporated into the productionprocess of diapers, either within the diaper or extra-diaper, asdesired.

The sensor assembly is constructed using manufacturing techniques andlayering similar to that used to manufacture feminine hygiene pads.

The material layers may be sheets, films, porous fabrics, coatings,gels, or the like. In one embodiment, two sheets of material comprisethe liquid management and absorbent layers are affixed to opposing sidesof the sensor. The layer materials may be chosen from any number ofmaterials, including polymers, waxes, gelatins and fibers.

Referring to FIG. 6, a sensor assembly 60 a in accordance with anembodiment of the invention includes a sensor 10 a located between aplurality of material layers. The arrows indicate the direction ofwetness flow towards from the wetness source toward the sensor assembly60 a. The sensor assembly 60 a includes a top layer 62, liquidmanagement layer 64, absorbent layer 66, and bottom layer 68.

In use, the top layer 62 will be placed closest to the wetness source.The top layer 62 is preferably made of spunbond polyester for allowingliquid to pass through to the material layers beneath it whileseparating conductive liquid, such as urine, from the user's skin. Thetop layer 62 provides the top surface and overall shape of the sensorassembly 60 a. The spunbond polyester material is commonly used as thetop layer in diapers.

The liquid management layer 64 is particularly advantageous as it isadapted to prevent the sensor 10 a from being triggered by ‘nuisanceevents’ such as moisture, humidity, urine drips, or sweat from the user.The liquid management layer 64 is preferably made of a water impermeablematerial such polyethylene or similar waterproof polymer. In theembodiment shown in FIG. 6, the liquid management layer 64 is smallerthan the top layer 62 and the absorbent layer 68 to allow liquid to moveto the absorbent layer 68.

As mentioned above, the liquid management layer 64 allows for greaterfunctionality of the sensor assembly 60 a. Because it protects thesensor 10 a from direct wetting, it can allow for prevention of falsealarms due to nuisance or small-volume wetness events.

Furthermore, the liquid management layer 64 also provides a degree ofcontrol in liquid sensing. In conjunction with the absorbent layer 66,the liquid management layer 64 allows for control over the amount ofliquid needed to trigger the sensor 10 a to send a signal 12 reporting awetness event. In an embodiment in which the sensor 10 a is sandwichedbetween the liquid management 64 and absorbent layers 66, the amount ofliquid necessary to trigger the sensor 10 a to send the signal 12 isrelated to the size of the liquid management layer 64. A smaller liquidmanagement layer 64 will allow liquid to reach the absorbent layer 66 ata position closer to the sensor 10 a than would a larger layer.

The liquid management layer 64 may be of a number of shapes, geometries,and patterns that can enhance the degree of liquid sensing control. Itcan be shaped to help guide liquid towards the sensor 10 a regardless ofthe user's spatial orientation. For example, it may have a number ofopen sections nearer to the sensor to act as an inlet for liquidabsorption, especially in cases where the absorbent layer 66 a might beimpeded from distributing liquid to the sensor 10 a. Thus, if a liquidinsult occurs away from the sensor 10 a, especially for male users, theliquid management layer 64 drains the liquid towards the sensor 10 a.

The liquid management layer 64 may be composed of semi-permeablematerials that can greatly limit liquid flow and prevent or delay theabsorbent layer from saturating with nuisance wetness events such astrickles or small volume voiding. Alternatively, it may be a combinationof layers of absorbent materials and liquid impermeable materials toabsorb wetness but prevent direct wetting of the sensor 10 a. The liquidmanagement layer 64 is preferably made of one or more polymers selectedfrom polyesters, polyethylenes, polypropylenes, polystyrenes, acrylates,or other water-impermeable materials.

The size of a particular layer is contingent upon the amount of wetnessto be sensed, the wetness area, and the material from which the layer ismade. In general, the liquid management layer 64 is either smaller thanthe absorbent layer 66 but larger than the sensor 10 a or has a porousor open structure that directs liquid to wet the absorbent layer 66 atspecific sites. Liquid wetted directly atop the liquid management layer64 traverses the surface of the liquid management layer 64 and wets theunderlying absorbent layer 66, which subsequently wets the sensor 10 a.The liquid management layer 64 may also be used only to prevent directwetting of the sensor 10 a and liquid, but otherwise allowing theabsorbent layer 66 to be wetted first.

The liquid management layer 64 may have holes in it to allow themajority of the conductive liquid to flow through it, essentiallyleaving only a mesh of material to collect fluids. This prevents fluidfrom accumulating at the sensor 10 a.

The liquid management layer 64 may have fluid wicking arms/threads/tubesthat collect fluid from a large area and draw it toward the sensor 10 a.

In this embodiment, the sensor 10 a is located between the liquidmanagement layer 64 and the absorbent layer 66. The sensor 10 a isoriented with the back side of the substrate 20 contacting the liquidmanagement layer 66. The side of the sensor 10 a on which the sensorcircuitry is located abuts the absorbent layer 66. This orientationallows for the leads 26, 28 to be wetted by conductive liquid in theabsorbent layer 66.

In this embodiment, the substrate 20 is preferably less than 200 mm² inarea. The leads 26,28 are made, respectively, from silver phosphate andmagnesium. The leads 26,28 preferably have an area less than 9 mm² andare less than 0.25 mm thick. The antenna 32 is preferably made fromsilver particle ink printed onto the polyester substrate.

The absorbent layer 66 is preferably made of a hydrocolloid-type ofmaterial that swells when it absorbs water such as the hydrocolloidmaterials used in conventional diapers. Suitable materials capable ofachieving this function include cellulosic materials. The absorbentlayer 66 wicks the conductive liquid toward the sensor 10 a.

The absorbent layer 66 allows for a wide area of sensing using a singlesmall sensor 10 a. The absorbent layer 66 effectively acts to transportliquids from remote areas of the sensor assembly 60 a to the sensor 10a. Materials with rapid wicking or capillary properties, such as lateralflow strip material, are ideal for this embodiment. This allows forlonger distance sensing than would be normally available.

Dryness sensors can be used in bags that empty rather than fill. Thewicking agent can allow continuous transport of liquid in to a reservoiror additional absorbent layer. When liquid is no longer available, thewicking material empties and no longer signals liquid at the site.

The absorbent layer 66 may be made of liquid retaining materials thatallow for the collection of small amounts of liquid and moisture overtime. The liquid continually migrates towards the sensor 10 a asadditional liquid is collected. When enough liquid has been collected,the sensor 10 a is triggered and a signal 12 is transmitted to thedetector 14. Thus, a user whose enuresis is in the form of minor wettingevents may also allow a wetness signal to be triggered after sufficientwetting even when no singular wetting event may be sufficient fortriggering a signal.

The bottom layer 68 is preferably made of the same material as the toplayer 62 and is the same size as the top layer 62. The bottom layer 68allows liquid to pass through to the undergarment beneath and providesthe bottom surface for the sensor assembly 60 a. If desired an adhesive70 may be applied to the bottom layer 68 for affixing the sensorassembly 60 to a undergarment 72 such as a diaper. If the sensorassembly is to be used in conjunction with standard diaper, the bottomlayer 68 is preferably made of spun bonded polyester with hydrophiliccharacteristics. If, however, the sensor assembly 60 a is to be usedwith a standalone liquid absorbing product, such as a undergarmentinsert, the bottom layer 68 is preferably made of propylene resinwithout any added surface surfactants. This cloth-like film preventsleakage out of the sensor assembly 60 a.

Other arrangements of the sensor assembly are also possible. Referringto FIG. 7, in an alternative embodiment of the sensor assembly 60 b, thesensor 10 a is incorporated into the absorbent layer 66 and the liquidmanagement layer 64 is placed atop the absorbent layer 66 b. The bottomlayer 68 is located on the side of the absorbent layer 66, that isopposite the liquid management layer 64.

Referring to FIG. 8, in another alternative embodiment of a sensorassembly 60 c, the liquid management layer 64 encompasses the sensor 10a and absorbent layer 66. In this embodiment, the liquid managementlayer 64 preferably includes minimally porous, swellable, or slowlydegrading/dissolving materials, or any other materials that retard theflow of liquids without completely blocking them. Alternatively, theliquid absorbent layer 66 may encompass the liquid management layer 64to prevent liquid from pooling over the liquid management layer 64.

In yet another preferred embodiment of a sensor assembly 60 d shown inFIGS. 9 and 10, the liquid management layer 64 overlaps the absorbentlayer 66 but follows its general shape and contour. A plurality ofperforations 90 penetrate the liquid management layer 64 for allowingliquid to drain through the liquid management layer 64 towards theabsorbent layer 66 in proximity to the sensor 10 a. The arrows in theperforations 90 in FIG. 10 illustrate the direction of liquid flow. InFIG. 9, the liquid management layer 64 is shown as being transparent inorder to provide an understanding of where the sensor 10 a is located.

The dimensions of the sensor 10 a used in the sensor assembly may beadjusted as desired. Referring to FIG. 11, a sensor assembly 60 e inaccordance with an alternative embodiment of the invention includes theelongated sensor 10 b, the top layer 62, liquid management layer 64,absorbent layer 66, and bottom layer 68. This configuration is usefulwhere the wetness area is large and the sensor assembly 60 e replaces afeminine hygiene pad or acts as an insert for a female or child's diaperor panty.

The various embodiments of the sensor assembly are particularly usefulas wetness detecting inserts for undergarments, including adult or babydiapers or briefs. FIG. 12, shows a diaper 100 with a sensor assembly60, which could be any of the sensor assemblies 60 a-f described herein,located in the crotch region thereof on the interior side of the diaper100. The sensor assembly 60 may be attached to the diaper 100 using anattachment mechanism 36 as described previously.

Shown in FIG. 13 is a diaper 100 with two sensor assemblies 60 locatedin the crotch region. This configuration may be advantageously employedin large diapers such as large adult male diapers. In the example shownin FIG. 13, the sensor assemblies 60 are preferably the elongated sensorassembly 60 e described in connection with FIG. 11 or the sensorassemblies described in connection with FIG. 14 below.

FIG. 14 shows an embodiment of the sensor assembly 60 f that isparticularly useful in this situation because it allows for the wetnesssensing area to be very large. In an exemplary embodiment, the wetnesssensing area is about 30 cm long and about 10 cm wide. The sensorassembly 60 f construction is similar to the embodiment described inconnection with FIG. 11 but with an added acquisition and distribution(ADL) layer 110 to control the flow of liquid toward or from the sensoror sensors as desired. The ADL layer 110 is conventionally used in manydiaper designs. It is located above the absorbent layer 66 f to moveliquids to avoid leakage. In those cases where it is desirable todifferentiate between an insult coming from the front of the diaper andan insult coming from the back of the diaper, multiple sensors 10 b canbe used and the ADL layer 110 is helpful in keeping those liquidsseparated.

C. Wetness Sensor Integrated into Undergarment

Referring to FIG. 15, another aspect of the invention is a undergarment120 such as a diaper or brief having one or more sensors 10 integratedtherein. A typical example of the undergarment 120 construction, showinghow a sensor 10 is integrated therein is best seen in the cut-away viewof the undergarment 120 a in FIG. 16. The sensor 10 may be any of thesensor embodiments described herein. The undergarment 120 a includes aplurality of many of the same material layers described in connectionwith the sensor assemblies. The undergarment 120 a acts like a diaper todirect liquid away from the skin of the user and store it in anabsorbent material. In such embodiments, therefore, the sensor 10 b isincorporated into the material layers used to make the undergarment 120a. Accordingly, rather than being a undergarment 120 a insert like thesensor assemblies, the undergarment 120 a has the sensor 10 b built in.

The undergarment 120 a includes a top layer 62, ADL layer 110, absorbentcore 122, fluid management layer 64, sensor 10 b, and an absorbent layer66. The top layer 62 is preferably made of hydrophilic nonwovenpolypropylene material. It allows the moisture to proceed through to theunderlying layer while giving the user the feeling of dryness. The ADLlayer 110 is typically located near the wetness source where urine ismost likely to be deposited. The ADL layer 110 is in the form of a patchthat spreads and/or moves liquids very quickly into the absorbent 66layer and reduces the potential for leakage. The use and/or choice ofmaterials used in the ADL layer 110 depends on the materials chosen forthe absorbent layer 66. Typical ADL forming materials are resin bondednonwovens, air bond nonwovens, “curly” fibers found in certain “highloft” configurations like aperture film made of perforated plastic. Thislayer typically has a blue color when used in current diaper/briefmanufacturing.

The absorbent core 122 is preferably made of a cellulosic pulp derivedfrom pine trees or polypropylene-based synthetic fibers. It is oftendispersed with super absorbent polymer (SAP) for extra liquidabsorption. The thinner the absorbent core 122, the more important theADL layer 110 becomes for distributing moisture throughout the surfacearea to avoid clogging of the absorbent core 122. In this arrangement,the sensor 10 b is preferably oriented such that the leads 26, 28directly contact the fluid management layer 64. The substrate 20 ispreferably a semi-permeable material designed to intercept smallquantities of liquid from getting to the sensor 10 b. This eliminatesfalse alert signals due to sweat or minor wetness events. The liquidmanagement layer 64 overlaps the sensor 10 b in such a way as to forceliquid to move beyond its periphery and into the absorbent layer 66prior to the liquid coming into contact with the leads 26, 28. The fluidmanagement layer 64, then, controls the speed and quantity of liquidthat eventually reaches the leads 26,28.

FIG. 17 is cut-away view of another embodiment of an undergarment 120 bconfigured for those applications where the undergarment 120 b will beworn throughout the night, thereby leading to the expectation that theundergarment 120 b will be subjected to multiple urine insults. Thisembodiment includes a mechanism for liquid storage and release, therebyallowing for multiple insults to be monitored from a single sensor. Whenthe undergarment 120 b is wetted, the liquid is first stored in one ormore liquid retention zones (chambers, etc.) until it can be releasedinto the absorbent layer 66. A sensor 10 b is in contact with thisliquid retention zone and signals an insult. Once all the fluid isdesorbed from the chambers, the sensor 10 b stops transmitting signals.Upon rewetting, the sensor 10 b once again transmits a wetness eventsignal. This process is repeated until the sensor 10 b is removed fromthe wetness zone.

The embodiment of the undergarment 120 b of FIG. 17 utilizes a number oflayers that constitute a fluid storage and release mechanism. Itincludes a top layer 62, an ADL layer 110, a liquid retention layer 124,a sensor 10 b, and an absorbent layer 66. The top layer 62 allows liquidto penetrate, thereby giving the individual the feeling of dryness. Theliquid then moves to the ADL layer 110, where it is distributed over alarge area to avoid clogging the absorbent layer 66 immediately belowthe point of liquid incursion. After passing through the ADL layer 110,the liquid penetrates the liquid retention layer 124.

The liquid retention layer 124 is preferably made from plastic filmhaving a plurality of apertures 126 formed therein. The sensor 10 b isoriented such that the galvanic cell 24 directly abuts the liquidretention layer 124. The void spaces surrounding the apertures 126 catchlarge volumes of liquid until the liquid can be absorbed by theabsorbent layer 66 located below the sensor 10 b. When the liquidcontacts the leads 26,28 the galvanic cell 24 generates electricity forsending a wetness alert signal to the detector 14. If the volume ofliquid is sufficient, the sensor 10 b sends the wetness alert signal.When the liquid is finally absorbed by the absorbent layer 66, thegalvanic cell 24 becomes inactive until it is contacted by liquid from asubsequent insult.

To increase the voltage and/or current output of the galvanic cell 24,the concentration of ionic species in the wetting liquid can beincreased by incorporating cationic and/or anionic salts into one ormore of the material layers of the undergarment or sensor assembly. Thecationic salts may include, but are not limited to, Na, K, Al, Fe, Ca,Au, and/or Ag salts. The anionic salts may include, but are not limitedto Cl, F, Br, sulfate, phosphate, and/or nitrate salts. In a preferredembodiment, one or more salts are incorporated into the absorbent layer66 in the vicinity of the sensor 10 a,b. In the alternative, the one ormore salts are added directly adjacent to the galvanic cell 24 in anadhesive matrix that can become wetted in the presence of liquid.

The sensor 10 a,b may be built inside a diaper during the diapermanufacturing process. For example, the sensor 10 a,b may be added tothe diaper's impermeable lining or atop the permeable fluid pass-throughlayer. Excess fluid not absorbed by the absorbent layer may pass ontothe permeable layer and into the diapers wetness control system.

Additionally, using new electronic printing technology, the sensor 10a,b may be printed onto or into the diaper during diaper manufacturing.

Depending on the size and desired target area for wetness, more than twosensors and/or sensor assemblies may be used.

D. Computer-Based Wetness Monitoring System

The sensors, sensor assemblies, and sensor integrated undergarmentsdescribed above are particularly useful when employed in a computerbased wetness monitoring system. The inventors have developed a computerbased wetness monitoring system that may be used by a monitoring agent,such as a caregiver, to monitor the wetness of a child or a patient, forexample. A preferred system, in accordance with an aspect of theinvention, allows the caregiver to receive an alert signal when awetness event, such as urination or defecation, occurs, thereby allowingthe caregiver to respond to the event quickly. As is described ingreater detail below, one or more of the wetness sensors are affixed tothe item to be monitored in such a position as to allow the one or moresensors to be insulted with the liquid to be detected. Areceiver-transmitter (transceiver), assigned to detect electromagneticsignals from the wetness sensor is located within detection range of theRF signal transmitted from the wetness sensor. The transceiver isprogrammed with information specific to the item being monitored. When awetness sensor is insulted, the galvanic cell powers the sensor and thesensor subsequently transmits a series of data to the transceiver. Thedata may include a code specific to the insulted wetness sensor, datarepresenting the state or value received from the sensor, position ororientation information when available, and other data associated withthe wetness sensor. The transceiver passes this data along with itsidentification to a remote database. The system may then be initializedand ready for the next wetness event or can wait until the wetnesssensor or monitored device (e.g. diaper) is replaced beforereinitialization. The transceiver may be worn by the user and placedremotely from the user.

Referring to FIG. 18, a wetness monitoring system 200 in accordance withan aspect of the invention includes a wetness sensor 10, a transceiver202 and a control computer system 206.

When the sensor 10 detects a wetness event, it generates and transmitsdata packets 208 separated by a time interval T, containing data aboutthe wetness event to the transceiver 202. The transceiver 202 is alsocapable of sending a transceiver signal 210 to the sensor 10. In manyimplementations of the wetness monitoring system 200, the sensor 200 isassociated with an undergarment 220 worn by a user.

The transceiver 202 and control computer system 206 are able tocommunicate data back and forth via a network 204. The network 204 maybe an internet network and/or ethernet network, for example.

A monitoring agent 205 is capable of communicating with the controlcomputer system 206 via the network 204. This allows the monitoringagent 205 to receive wetness event alerts from the control computersystem 206. Monitoring agents 205 include but are not limited to patientor child caregivers such as medical personnel or parents, and any otherparty that is interested in receiving an alert when a sensor isactivated.

The control computer system 206 includes an interface 212, machinereadable memory 214, and database 216. The control computer system 206and its interface 212 and database 216 are realized by at least oneprocessor 218 executing program instructions stored on the machinereadable memory 214. The system 200 is not limited to any particularnumber, type, or configuration of processors 218, nor to any particularprogramming language, memory storage format or memory storage medium.

In implementations of the control computer system 206, the wetnessmonitoring system 200 is not necessarily limited to any geographicallocation or networking or connection of the processors and/or storagemedia, provided that the processors and/or storage media are capable ofcooperating to execute the interface 212 and database 216. It is notrequired that the processors and/or storage media be commonly owned orcontrolled. Additionally, although the database 216 is referred to hereas a single database, it is not necessary that it be located on a singlememory media unit or at a single physical location. The database 216 maybe divided into sub-databases for categorizing information if desired.

The database 216 includes information about the user, such as, forexample, the user's identification, vital statistics, and wetness eventhistory. It also includes information transmitted from the sensor 10 tothe transceiver 202 regarding wetness events registered by the sensor10. Data may be entered manually into the database 216 via the interface212, which is a network connectable electronic device such as acomputer, tablet computer, personal data assistant, mobile telephone, orthe like.

Referring to FIG. 19, the system 200 is initiated via an initiationprotocol 228. At block 230 the transceiver 202 is associated with a userand a particular sensor 10 or group of sensors being worn by the user.This allows the control computer system 206 to open a user data file inthe database 216. Data transmitted from a sensor 10 worn by the user tothe transceiver 202 is stored in that particular user's data file.

By way of example, this may implemented in an institutional setting bymanually entering information about the user via the interface 212,including the user's identification and room number or location at theinstitution. The user is then assigned a transceiver 202 configured tocommunicate with the sensor 10 worn by the user.

At block 232, the transceiver 202 is placed in the user's room and thenetwork connection between the transceiver 202 and database 216 isverified by pressing a button on the transceiver 202.

At block 234 the transceiver 202 communicates data to the database 216via wireless repeaters placed throughout the institution to detect datatransmissions from all of the various transceivers 202 assigned to otherusers at the institution. The initial data stream from the transceiver202 to the database 216 reflects that fact that that it is aninitialization data transmission. The initial data stream may alsoreport the battery condition of the transceiver 202. At block 236, thecontrol computer system 206 sends an ACK response to the transceiver202.

An added benefit of placing different transceivers 202 throughout theinstitution is that, should the user move to a different location in theinstitution, an alternate transceiver 202 will detect the user'smovement and provide a form of user geo-tracking within the institution.When multiple sensors 10 are concurrently transmitting data through acommon transceiver or multiple transceiver are operating in closeproximity, data transmission is achieved using anti-collision RFprotocol.

Moving now to FIG. 20, a user preparation protocol 237 in accordancewith an aspect of the wetness monitoring system 200 begins at block 238where the sensor 10 is attached to the user in the form of an individualsensor attached to the user's undergarment 220, a sensor assembly 60placed in the user's undergarment, or an undergarment 120 having asensor 10 integrated therein. At block 240, the transceiver ispowered-on and begins communication with the database 216. At block 244,the transceiver 202 transmits a transceiver identification signal to thedatabase 216, allowing the control computer system 206 to identify theappropriate user data file. The control computer system 206 subsequentlyrecords the identification, date, Lime, and reason for the transmissionin the user data file (block 246) and the transceiver receives an ACKresponse (block 248). The transceiver 202 then enters stand-by modewhile waiting to receive a signal from a sensor 10.

FIG. 21 outlines a wetness detection and reporting protocol 252 inaccordance with another aspect of the wetness monitoring system 200.When user urinates or deffocates, a wetness event occurs (block 254) andthe liquid eventually comes in contact with the galvanic cell 24 (block256), which powers the sensor 10 (block 258). The sensor 10 transmits awetness event signal to the transceiver 202 (block 260) the transceiver202 subsequently receives the signal (block 262). The transceiver 202then communicates the wetness to the database 216 (block 264) andreceives an ACK response (block 268) from the control computer system206, acknowledging that the data was received by the database. 216 Dataabout the wetness event that is recorded in the database 216 includesthe date, time, and information about the wetness event. The transceiverreverts back to stand-by (block 270). If another wetness event occurs,the detection and reporting protocol 252 is repeated.

In accordance with yet another aspect of the wetness monitoring system200, after a wetness event, the wetness alert protocol 272 in FIG. 22may be initiated. In the alert protocol 272, one or more monitoringagents receive an alert indicator (block 274). The alert indicator maybe in the form of an electronic message such as an email or SMS messagesent by the control computer system 206 to the monitoring agent'snetwork connectable electronic device and/or an audible alarm. Themonitoring agent may then service the sensor 10 user (block 276) byengaging the user, removing the soiled undergarment, and replacing thesoiled undergarment with a new undergarment equipped with a sensor. Themonitoring agent then resets the transceiver 202 (block 278) by, forexample, pressing a reset button on the transceiver 202. The transceiver202 subsequently reports to the control computer system 206 that thecorrective action was taken (block 280) and receives an ACK response(block 300) from the control computer system 206, acknowledging that thedata was received by the database 216. When the new sensor 10 isattached to the user, the system then 200 reverts back to the initiationprotocol 228.

The transceiver 202 may be pre-programmed to define the number ofwetness events that must occur and/or the number of sensors that must betriggered before an alarm indicator is sent. This allows the monitoringagent to configure their particular application as they choose.

If the transceiver 202 is equipped with a GPS unit 132, accelerometer134, and/or other electronic component such as a temperature sensor, thetransceiver 202 may transmit location, accelerometer, and/or temperaturedata to the transceiver control computer system 206. Preferably, toavoid false alarms, the transceiver is pre-programmed only to send suchdata to the control computer system 206, when the data fall outside ofcertain atypical parameters. When an atypical reading occurs, however,the transceiver 202 transmits a signal to the control computer system206 indicating the transceiver's 202 identification and reason for thetransmission. The transmission is then recorded in the database 216. Thecontrol computer system 206 may subsequently send an alert indicator tothe monitoring agent.

With respect to the accelerometer 134, because a user will typicallymove around often during the awake periods and seldomly during sleep,accelerometer 134 movements will become more predictable based on themovement history of the user. When the transceiver 202 is equipped withan accelerometer 134 transmits to the control computer system 206 anatypical movement such as a fall or sudden vibration, the controlcomputer system 206 stores the information transmitted in the user datafile. In addition, normal nocturnal movements of the user are typicallyindicative of normal sleep patterns. When these movements change beyonda pre-defined threshold, it can indicate a problem, unknown to themonitoring agent, that the user is experiencing. Events such assleepwalking and falling out of bed or continuous movement while in bedcan be detected by the accelerometer 134 as an indication of the needfor immediate attention.

The database 216 may include one or more predictive algorithms designedto predict a subsequent wetness event based on a user's previous wetnessevents. In this case, the control computer system 206 may send an alertindicator to the monitoring agent, alerting the monitoring agent of thelikelihood of an impending wetness event, giving it the ability topreclude said event by taking corrective action in advance. Predictivealgorithms may utilize a variety of information including: subjecttoileting and wetting history, subject recent activity levels (e.g.sleep, wake, active), recent subject locations (e.g. cafeteria, bed,coffee shop), subject orientation, and subject-specific history andphysical information that may be stored in the database 216.

E. Odorant Sensing

In another aspect of the invention the wetness sensor is replaced withan odor sensor. Is this aspect, the arrangement of the previouslydescribed sensor assemblies, undergarments with integrated sensors, andthe operation of wetness detection system are the same, except for thefact that the signal is transmitted to the detector in response to anodor, rather than wetness. The odorant (a chemical tag added to thewetness absorbing article) may include a number of scented or unscentedvolatile chemicals, including alcohols, ketones, thiols, esters, etc.The odorant is detected using a chosen sensor, which may be selectedfrom among surface acoustic wave (SAW) sensors, metal-organicsemiconductor (MOS) sensors, field effective transisitors (FETs), orchemoresistive sensors. The odorant causes a change in the physical orchemical state of the sensor which can be read and interpretedelectrically by the sensor reader. The sensor device may have an odorantfilter selective to the given chemical to be detected. The odorant maybe chosen among those most unlike odors found in health facilities toprevent false positives.

An odorant that interacts with the chosen insult is first applied to awetness absorbing article. An external odorant sensor, such as a MOSsensor, is powered and set to detection mode. As fluid is dischargedinto a wetness absorbing article, the fluid releases (via chemicalreaction, dissolving of protective coating, aerosolization, etc.) theodorant gas into the surrounding article space. As the gas escapes fromthe article, the external sensor is triggered at a pre-determined in-airconcentration to signal the presence of the insult, indicating that thearticle must be changed or attended to.

In one embodiment, the odorant comprises alcohols entrapped within awater-dissolvable matrix. As urine passes over the matrix due to anincontinence event, the alcohol is released into the atmosphere. Asensor-transceiver worn by the patient on the diaper is triggered to theactive signaling state by the presence of the alcohols in the environsand signals to the detector that a wetness event has occurred.

Decomposition products of urine, such as ammonias, may be chosen as theodorants. Various chemicals that hasten the production of suchdecomposition products may also be used to increase the concentration ofthe odorants at the sensor. The decomposition products of urine frombiological decomposition factors, such as bacteria, can also be used asthe odorant.

The odorants may be incorporated anywhere within an undergarment, suchas a diaper, from the back-liner to the top layer. The odorant may bestrategically placed within the garment to reflect wetting patterns. Inthe case of a diaper, should the caregiver desire that only full diapersbe changed, the odorant may be placed only at the extremes of the diapergeometry, such as at the waist or along the edges of the article. Inthis manner, initial fluids will be absorbed in the central absorbentlayers of the diaper. As the diaper reaches fullness, fluid will beforced to distribute to the edges of the garment where the odorantresides, thus triggering the odorant sensor and transmitting a wetnessevent as described herein.

Multiple odorants or taggants may be utilized to determine the locationand/or level of saturation of the diaper. This information may be usefulin predicting incontinence events since it will provide information eachtime an incontinence event occurs, along with a relative volume alreadyabsorbed in the diaper. Additionally, the quantity of taggants detectedat the sensor may provide flow or volume information.

The chemical sensor may also be able to directly detect the odor fromthe event (urine or fecal matter), breakdown odors, or byproducts of theevent interacting with the diaper without the need for a taggants orodorant added to the diaper.

The odorant may cause a physical change outside of typical electronicchanges found in many sensors. In one embodiment, the sensor consists ofa color/pattern change material and an optical detector. The colorchange may be from one hue/saturation/value to another or the colors mayshow up in a pattern that can be read similar to a barcode. The colorchange material may be in a state of permanence (replaceable), may lastfor a chosen duration, or may be reversible where the caregiver canreset the color/pattern change via application of voltage, current,chemicals, physical pressure, magnetization, or other means.

The optical detector may be a colorimeter, spectrophotometer, UV-Visspectroscope, optical imager, pattern detector, barcode scanner, or thelike. The optical detector periodically scans the color/pattern changematerial to conserve battery power. The optical detector may be separatefrom the wetted article or it may be applied to the article surface. Inone embodiment, the optical detector is attached to the back of adisposable article and the color change is measured directly from thearticle. The monitoring agent is also presented with an opticalmechanism of identifying wetness alongside with the electronicmechanism.

F. Sensor in Liquid Collection Bag

The sensor 10 a,b may be placed into a liquid collection bag, such as aurine or other waste collection bag, or a fluid supply bags to indicatethe presence of fluid in the bag. This can be used to determine when thebag is full or empty. Multiple sensors 10 a,b built into the bag can beused to determine the rate of filling or percentage of fullness based onthe timing of the firing of the sensors 10 a,b. Furthermore, a singlesensor 10 a,b with a degree of wetness detection mode can also be used.

Referring to FIG. 23, in accordance with an aspect of the invention, aliquid collection bag 400 includes a bag interior 402 defined by aplurality of bag interior walls 404. Three wetness sensors 10 arevertically spaced apart along one of the interior walls 404 fordetecting the level of liquid 408 in the bag 400

The sensor 10 a,b configuration implemented into collection bags canmake use of the fluid management layer 64 and absorbent layer 66. Toavoid wetting the sensor 10 a,b from incoming fluid drops or splashes,the fluid management 64 and absorbent layers 66 may take on a number ofconfigurations. In one embodiment, the absorbent layer 66 is a thinmembrane that runs the length of the collection bag while the fluidmanagement layer 64 is a sheath that surrounds the sensor. The absorbentlayer 66 absorbs sufficient fluid to trigger the sensor 10 a,b at agiven fluid height in the bag, signaling fullness. Fluid containers forlubricants, hydraulics, as well as blood or IV fluid are of the numerousapplications for this concept.

Because the sensors 10 a,b are inexpensive and shelf life of thegalvanic cell 24 is very long, the sensors 10 a,b can be built into thebags and remain inactive until wetted. A transceiver 202 may be attachedto a bedside pole or other location to facilitate communication withother electronic devices to indicate problems or maintenancerequirements (e.g. replace bag). The transceiver 202 may also be builtinto an existing monitor, such as an integrated patient monitor like aPhilips Intellivue system.

G. Wound Care

Similar to wetness detection in a diaper, detection of moisture in awound dressing is also important. In another aspect of the invention,one or more of the wetness sensors 10 a,b are embedded into or attachedto a wound dressing to indicate the presence of moisture or the amountof moisture present under or in the bandage. The sensor 10 a,b maycommunicate with a transceiver 202 that communicates with a database 216as described above. In the wound care application, differentiationbetween different fluid types such as blood, sweat, or pus for example,may provide additional information about the status of the wound (e.g.infected, healthy, actively bleeding).

Referring to FIG. 24, a wound dressing 410 in accordance with an aspectof the invention, includes a wetness sensor 10 attached thereto.

Ion-selective electrodes that utilizes polymers such as PVC orpolyurethane can detect a number of cations and anions. Furthermore,selective enzymatic coatings may be applied to selectively sensediaminobutanes and other chemicals that may signal necrosis due toinfection. Such sensors may be worn as a wound dressing or as a simplertest strip.

Pathogenic bacteria or other infectious agents can themselves be sensedthrough the use of coatings, membranes, or antibody/antigen pathways.Microbial response in such a system is tested by ion transport through abilayer lipid membrane-coated solid state electrode allows forselectivity and decreased source resistance in the electrode assembly,which is then captured by the sensor electronics and transmitted in thedata stream or burst timing. Other embodiments include using biologicalrecognition components such as receptors, nucleic acids, and antibodieswith the appropriate transducer. Potentiometric and amperometric designsmay also be implemented.

H. Lateral Liquid Flow Test Strip

The wetness sensor 10 a,b may be incorporated into a lateral flow teststrip or immunoassay to detect the presence of an analyte fluid. Thissame sensor may be configured to detect and transmit the results of theassay to the transceiver 202 and on to the database 216.

I. Temperature Sensing

Materials with various solid-liquid transition temperatures can beplaced on or with the wetness sensor 10 a,b to enable temperaturesensing. When the material reaches its melting temperature it will turnto liquid which will activate the sensor 10 a,b. As describes above, thesensor 10 a,b then transmits a signal to the transceiver.

Suitable materials include materials, mixtures, and compounds withadjustable solid-liquid transition temperatures depending on thematerial composition including can be eutectic, peritectic, orpressure-sensitive phase transition materials.

This aspect of the invention may be used to determine when a box, crate,device, or item exceeds a certain temperature. This may be useful forapplications that require very careful temperature control such as foodstorage, organs for transplant storage, and storage of organic or othersamples for testing.

J. Moisture Sensing in Materials or Air

A number of desiccants and other hygroscopic materials absorb humidity.For example, some gels, gelatins, acrylates, and other materials readilyabsorb moisture. Because the sensors 10 a,b function using very lowpower, this allows the sensor 10 a,b to generate a voltage and currenteven in partially-wetted environments if a conductive path through thehygroscopic material or moisture absorbent material is available.

This is also useful for testing condensation that may accumulate over aperiod of days. The sensor 10 a,b may act as a high humidity sensor, anair leakage sensor, in an airtight container, or for many otherpurposes.

K. Pressure Sensing

A pressure sensor can be created by augmenting the wetness sensor with asmall packet of liquid that is adapted to be released when pressure isapplied to the packet. This packet may contain salt water and be made ofdifferent materials and construction to optimally trigger the sensorwhen a desired pressure is achieved.

Additionally, this configuration may be used to activate the sensor“upon demand” by simply squeezing the packet manually or with amechanical device. The release of the liquid allows the sensor 10 a,b toremain wet for many hours, which prolongs the ability of the sensor 10a,b to transmit data to the transceiver 202. For example, thesensor/liquid-packet combination may be placed on surgical sponges forallowing the packet to be broken just before use. The sensor 10 a,b onthe sponge will transmit data continuously while in use. The sponge maythen be placed in a metal container to “silence” the transmission uponremoval from the body. Additionally, the liquid may be removed by asecond process (either drying, removal, or absorption) thus disablingthe sensor 10 a,b.

L. Hand Hygiene Monitoring

Another useful application of the sensor 10 a,b is in hand hygienemonitoring. In this example, a sensor 10 a,b may be placed on the hand,wrist, or finger (like a bandage, wrist strap, or ring). The sensor 10a,b will trigger and send a signal every time the hands come in contactwith soap or other fluids. This signal is transmitted to transceivers202 in various locations (soap dispensers, patient bed receivers,central stations) for monitoring compliance with hand hygiene protocols.

The invention has been described above with reference to preferredembodiments. Unless otherwise defined, all technical and scientificterms used herein are intended to have the same meaning as commonlyunderstood in the art to which this invention pertains and at the timeof its filing. Although various methods and materials similar orequivalent to those described herein can be used in the practice ortesting of the present invention, suitable methods and materials aredescribed. However, the skilled should understand that the methods andmaterials used and described are examples and may not be the only onessuitable for use in the invention.

Accordingly, this invention may be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure will bethorough, complete, and will fully convey the scope of the invention tothose skilled in the art. Therefore, in the specification set forthabove there have been disclosed typical preferred embodiments of theinvention, and although specific terms are employed, the terms are usedin a descriptive sense only and not for purposes of limitation. Theinvention has been described in some detail, but it will be apparentthat various modifications and changes can be made within the spirit andscope of the invention as described in the foregoing specification andthe appended claims.

That which is claimed is:
 1. A liquid sensor comprising: a liquidtransport layer positionable next to the skin of a wearer and capable oftransporting a volume of liquid discharged by the wearer away from thewearer's skin; a liquid absorbent layer that receives the transportedliquid; a sensor in liquid communication with the liquid absorbentlayer, the sensor comprising a substrate having a plurality ofelectrodes, a circuit, and a transmitter thereon; the plurality ofelectrodes being coupled to generate electrical power when in contactwith liquid; the circuit being electrically connected to the electrodesand configured to be activated by the electrical power, detect anelectrical parameter of the electrical power, and generate a pluralityof data packets indicating a degree of wetness corresponding to thedetected electrical parameter, store the electrical power until apre-determined electrical power value is met, and subsequently releasethe stored electrical power to the transmitter, wherein successive datapackets are separated by a time interval, the time interval beingproportional to the time required to reach the pre-determined electricalpower; the transmitter being electrically coupled to the circuit andconfigured to receive the plurality of data packets and transmitrepresentations of the plurality of data packets as electromagneticsignals.
 2. The liquid sensor of claim 1, wherein each successive datapacket is separated by a time interval, the time interval beingproportional to the detected electrical parameter.
 3. The liquid sensorof claim 1, wherein a data packet is generated when the electrical poweris released.
 4. The liquid sensor of claim 1, wherein the detectedelectrical parameter is selected from voltage, resistance, current, or acombination thereof.
 5. The liquid sensor of claim 1, wherein the degreeof wetness corresponds to an amount of liquid in proximity to theelectrodes.
 6. The liquid sensor of claim 1, wherein the substrate is aflexible electrical insulator and includes a generally planar surfaceand wherein the plurality of electrodes, circuit, and transmitter arearranged in a co-planar relationship along the generally planar surface.7. The liquid sensor of claim 1, wherein the substrate is elongatedalong a lengthwise direction, a first electrode includes a firstelectrically conductive wire extending along the lengthwise directionand a second electrode includes a second electrically conductive wireextending along the lengthwise direction.
 8. The liquid sensor of claim1, wherein the liquid sensor is positioned on an undergarment of a user.